An electric machine, such as a generator, typically comprises a rotor mounted for rotation within a stator frame. The rotor has a plurality of axially extending, circumferentially spaced slots in which field coils or windings are disposed. The coils are generally wound in a spiral configuration in the slots throughout the length of the rotor and are interconnected pole-to-pole by field connectors. Additionally, the end coils or end windings are connected to main lead terminals by main lead connectors, the main lead terminals, in turn, being connected to an outside excitation source, for example, through collector rings or brushes.
In a typical connection between a main lead terminal and the radially innermost end coil or winding, there is provided a main lead connector which extends generally radially from adjacent the rotor axis and makes a 180.degree. turn for connection with the innermost turn of the end winding. Particularly, the main lead connector extends radially outwardly, makes an approximately 90.degree. bend to extend in an axial direction and then makes a 180.degree. bend to extend in the opposite axial direction to underlie the innermost end winding to which it is connected, for example, by brazing. As will be appreciated, substantial inertial forces, i.e., centrifugal forces, are imposed on the windings and connectors at running speeds. These large forces can cause significant displacements of flexible conductors, e.g., the main lead connectors, as the speed increases from zero to synchronous speed, i.e., 3600 rpm, and back down to zero again during the start/stop cycles of the machine. The stresses associated with such displacements can lead to premature failure of the connectors, with a resultant long forced outage to replace the failed part.
More particularly, most current designs have no provisions for restricting the displacement of the main lead connectors. That is, there is no support for the main lead connectors at the substantial right-angle turn and 180.degree. turn of the main lead connectors for connection to the field end coils. The centrifugal forces acting on the turns of the main lead connectors tend to displace the connectors radially outwardly against the stack, causing stress and fatigue failures. A particular failure location occurs at the joint between the end of the main lead connector and the innermost end coil. It has been found that the radial outer end of the main lead connector bends radially outwardly, relaxes and bends outwardly again in response to centrifugal forces. Over time, stress causes the joint to break. Another area of significant stress is at the 180.degree. bend, as well as the right-angle bend. With multiple start/stop cycles, this stress can lead to cracks and actual breaking of the main lead connector. In certain designs, a flat-bottom block is positioned radially above the connector which has as a secondary function the positioning of the lead. However, the primary function of the flat-bottom block is to maintain the alignment of the coil stack. Accordingly, there has been a demonstrated need for a support block for limiting the deflection of the main lead connector to minimize stress and improve its fatigue life.